Download Chapter 1 community ecology

Community ecology
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Defintion - a natural assemblage of plants, animals and micro organisms inhabiting
a given habitat
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A group of population living in a unit area
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Community ecology is the study of co-existing, interdependent populations
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The major interactions within the community are competition, parasitism,
predation, mutualism and commensalism
Definition
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According to Clarke, a community is defined as “a group of mutually adjusted
plants and animals inhabiting natural area”
Example: Pond community: Plankton, plants, fishes, insects, crustaceans,
molluscas, worms, microorganisms and so on in a pond
Types of community
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Major community
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Minor community
Major community
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It is a large, self sustaining, self regulating and independent unit
Eg:- coral reefs, rocky community, mangroves etc.
Minor community
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It is smaller, not self sustaining and dependent on other communities for growth
and survival but it is found in major community
Example - Barnacles, Oysters, Algae, Polychaetes present rocky shores.
COMMUNITY ANALYSIS
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A procedure for investigating the structure, function and regulation of aquatic
communities and understanding of ecosystem functioning
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Methodologies based on biomass size, distributions, followed by food web
analysis, network analysis and dynamic simulation models
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Biomass size distributions provide a structural and energetic food web analysis
based on measurements of abundances and body sizes, and with a few general
assumptions mainly on size relationships of metabolic activities and
trophodynamics
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Food web analysis considers binary webs depicting qualitatively trophic links
between species or trophic guilds and provides profound information about the
food web structure
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Mass-balanced flow diagrams (trophic webs) take into account the magnitude of
flows between living and non-living compartments and provide comprehensive
descriptions of fluxes and cycling of matter and the trophic food web structure
when evaluated by network analysis
ECOLOGICAL DOMINANCE
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The ecological dominance is also known as the dominant species
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It refers to the most of population in a climax community
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Ecological dominance is the degree to which a species is more numerous than its
competitors in an ecological community or makes up more of the biomass
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Most ecological communities are defined by their dominant species
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In tropical coastal waters the dominant corals
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In temperate bogs, the dominant vegetation is usually species of Sphagnum moss.
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On earth, a large amount of its land ecosystems are dominated by human beings,
making human beings the ecologically dominant species over much of the planet.
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Tidal swamps in the tropics are usually dominated by species of mangrove
(Rhizophoraceae)
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Some sea floor communities are dominated by brittle stars.
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Exposed rocky shorelines are dominated by sessile
as barnacles and limpets.
organisms such
Community dominance
• A community has many species, of which one or few species play dominant role in
the community by virtue of their number, size and activities such species are called
‘Community dominance’
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The removal of community dominant from the community affects the community
drastically
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Species structure in most communities is either abundant or rare
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Few spices that are abundant
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Large number species that are rare
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The abundant species are called dominants. Eg. The mussel bed in the rocky shore
–Mytilus sp
Ecotone and edge effect
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Ecotone is the intermediate zone lying between two adjacent communities
Eg. An estuary is an ecotone lying between river and sea
Characteristics of ecotone
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The ecotone prevails environmental conditions intermediate to both two adjacent
communities
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The ecotone offers an abundance of food and shelter
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It contain organisms of both community
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As a rule ecotone contains more species often denser population than either of
the neighbouring communities. This is called edge effect
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The ecotone contain certain species which are completely restricted to this region
and they are called edge species
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The ecotone may be as broad as 100 km. or as narrow as 1 .0 km.
Ecological niche
• Niche refers to the functional status of an organism in its community
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According to Odum niche is the Profession of an organism in the community
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Habitat - address and niche – Profession
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Niche includes what it eats, how it behaves, how it responds to the environment
and interactions with other organisms in the community
Ecological niches may be
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Broad niche
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Narrow niche
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Narrow niches - the role or function in the community or ecosystem has more
finely subdivided and the species is specialized
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Specialized species are also called specialists Eg:- muddy, sandy , rocky etc.
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Broad niches - the species functions in the community is more of generalized
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They are either specialists or generalists with reference to the niche - Marine or
fresh water , estuarine organisms etc.
Ecological succession
• The process of development of new communities is called ecological succession
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“An orderly and progressive replacement of one community by another till the
development of a stable community in that area” (Smith, 1965).
Characteristics of succession
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The succession is caused due to the modification of the habitat
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The kinds of programs changes continuously with succession
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The diversity of species increases. biomass can also increases
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The first stage of community is ‘pioneer community’ The final stage of community
called ‘climax community’
Types of succession
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Primary succession – Bacteria, Lichens – first community (pioneer) on rocks –
biofilm
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Secondary succession-Attached of spats of barnacles, oyster, polychaetes etc. on
pioneer communities
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Autotrophic succession - Dominance of algae.
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Heterotrophic succession –
Dominance of heterotrophs
Climax community
• The terminal and persistent community in an ecosystem is called climax
community.
Animal are broadly grouped into
• R- selected species
• K-selected species